Communications And Tracking -
Review

After White's 40-minute presentation at the
FRR, Boris Nikitin gave a 10-minute summary of Group 4's activities.
Although he did not dwell on them, this group also had conducted an
important series of tests since the Mid-Term Review. First, they had
to establish that the spacecraft-to-spacecraft radio and cable
intercommunication systems would work without any interference from
internal or external power sources. In addition, they had to verify
the safety of the pyrotechnics used in the two spacecraft - for
example, the explosive bolts reserved for emergency undocking. To
prove that the radio waves from neither craft - especially from the
powerful Apollo high gain antenna used to communicate with the ATS-6
satellite could detonate those pyrotechnic components, Working Group
4 had directed a series of radiofrequency radiation experiments. All
of these tests had been favorably concluded. Just prior to the Flight
Readiness Review, R. H. Dietz and his fifteen teammates had
participated in the checkout of the American communication and
ranging equipment that had been installed into the prime and backup
Soyuz spacecraft and in electromagnetic compatibility tests of
American equipment scheduled to be transferred into Soyuz during the
mission.

Every spacecraft had its own electromagnetic
environment created by the sum of all the electronic and electric
components onboard. Just as an electric drill may affect television
reception or as a citizen's band transmitter may affect FM radio
reception, so too may the energy radiating from switches, fan motors,
or power cables interfere with television cameras or communications
gear. Electromagnetic compatibility (EMC) was not generally a problem
when one party developed its own equipment for use in its own
spacecraft. But the possibility of a problem with electromagnetic
interference might arise when equipment from one electromagnetic
environment was transferred to another. During January and February
1975, Soviet specialists had accompanied their counterparts to the
Kennedy Space Center to check out their television camera inside the
command and docking [299] modules for EMC.
And during May, the Americans had taken their television camera,
motion picture camera, headsets, microphones, and speaker boxes to
Baykonur to determine if the electromagnetic environment of Soyuz
interfered with their performance. The test team found that all the
American equipment operated satisfactorily. Although the Soviet half
of Group 4 had experienced some difficulty meeting project deadlines
before the Mid-Term Review, those problems had been resolved. Nikitin
could report at the ERR that all their joint work had been
completed.25

Academician Petrov had a few questions for
Nikitin. His main concern was radio receiver interference on the
Soviets' 121.75-megahertz frequency. During Soyuz 16, the crew
reported receiving broadcasts from commercial aviation sources
transmitting on that frequency. Petrov had asked the Americans to
help them get the international radio users to vacate that channel
during the mission, but NASA had decided not to take such an action.
So when Petrov asked Nikitin what plans had been made to deal with
such interference if it developed during the flight, the Soviet
chairman said that they would just try to identify the source and ask
the transmittor to suspend broadcasts during the remainder of the
mission. After some further discussion on this point, Walt Guy
reported on Working Group 5.26